The present invention relates to a new family of polyester polyurethanes film-forming resins, to a process for preparing them, to pseudolatices produced using said polyester polyurethanes resins and also to cosmetic compositions containing said pseudolatices.
It is common practice to use polyurethanes as film-forming resin in many cosmetic formulations, and in particular in different make-up products such as nail varnishes, mascaras and eyeliners. To be satisfactory, the resin must possess not only good film-forming properties, but also good staying properties, that is to say must be difficult to remove from its support by simply washing with water or by means of detergents.
In Patent Application EP 418,469, nail varnish compositions containing aqueous dispersions of aliphatic polyurethanes as film-forming resin have been described.
In Patent Application EP 391, 22, nail varnishes containing an aqueous dispersion of a polyurethane and/or of a polyurethane copolymer have also been described.
The use of these resins does not, however, enable compositions possessing good cosmetic properties to be procured, as a result, in particular, of a lack of staying power.
The present invention relates to polyurethanes and a process for preparing them. These polyester polyurethanes contain units corresponding to the following formulae (I) and (II): 
The polyester polyurethanes according to the present invention form pseudolatices and may be utilized as film-forming resin in cosmetic compositions.
It has now been found that, surprisingly and unexpectedly, a new family of polyester polyurethanes not only possess good film-forming properties, but also enable films possessing both great rigidity and excellent resistance to removal by water and detergents to be obtained.
It has been possible to obtain these excellent properties as a result of the particular choice of xcex1, xcfx89-dihydroxy polyester participating in the synthesis of the polyester polyurethanes according to the invention.
The polyester polyurethanes according to the invention make it possible to prepare pseudolatices which also have very good staying power and which, furthermore, are especially stable without the use of additional surfactants, in as much as they contain, in addition, ionic functions.
The subject of the present invention is, as a new industrial product, a polyester polyurethane containing units corresponding to the following formulae (I) and (II): 
in which:
R represents an alkylene or cycloalkylene radical or a bivalent aromatic radical having from 6 to 15 carbon atoms,
n represents an integer such that the molecular weight of the recurring unit is between 400 and 5,000,
R1 represents a bivalent radical chosen from the group consisting of;
(i) "Parenopenst"CH2"Parenclosest"m, m being an integer between 2 and 12, and
(ii) 
xe2x80x83the movable bond being in the ortho, meta or para position,
R2 represents a bivalent radical chosen from the group consisting of: 
R3 representing a hydrogen atom or a branched alkyl radical having from 1 to 3 carbon atoms,
R4 representing a hydrogen atom or a linear or branched alkyl radical having from 1 to 4 carbon atoms,
R5 representing a linear or branched alkyl radical having from 1 to 4 carbon atoms, and
p being 0 or 1, 
in which:
R is as defined above for the units of formula (I),
A represents an alkylene radical having from 2 to 20 carbon atoms, substituted with a carboxylic or sulphonic acid function, in salified or unsalified form, or interrupted by a tertiary nitrogen atom, the mole ratio between the units (II) and (I) being between 1:1 and 10:1, and preferably between 1:1 and 5:1.
The bivalent radical R of the unit of formula (I) is preferably chosen from the group consisting of hexamethylene, 4,4xe2x80x2-biphenylenemethane, 2,4-and/or 2,6-tolylene, 1,5-naphthylene, p-phenylene and 4,4xe2x80x2-methyl-enebis (cyclohexyl) radicals and the bivalent radical derived from isophorone.
The bivalent radical A of the unit of formula (II) is preferably chosen from the group consisting of: 
R6 representing a linear or branched alkyl radical having from 1 to 3 carbon atoms,
Y representing a carboxylic acid or sulphonic acid group or a salt thereof, and
t and q, which may be identical or different, representing an integer between 1 and 5, 
R7 representing a linear or branched alkyl radical having from 1 to 4 carbon atoms, and
r and s, which may he identical or different, representing an integer between 1 and 10.
The polyester polyurethanes according to the invention can, in addition, contain units corresponding to the following formula (III): 
in which:
R is as defined above for the units of formula (I),
B and Bxe2x80x2, which may be identical or different, represent xe2x80x94Oxe2x80x94 or xe2x80x94NHxe2x80x94, it not being possible for B and Bxe2x80x2 simultaneously to represent xe2x80x94Oxe2x80x94, and
X represents an alkylene or cycloalkylene radical having from 2 to 12 carbon atoms or a hivalent aromatic radical having from 6 to 12 carbon atoms,
the said unit being present in a proportion such that the mole ratio of the sum of the units of formulae (II) and (III) to the units of formula (I) is an integer between 1 and 10, and preferably between 1 and 5.
The molecular weight of the polyester polyurethanes according to the invention, measured by steric exclusion chromatography, is generally between 4,000 and 500,000, and preferably between 6,000 and 200,000.
The subject of the present invention is also the process for preparing said polyester polyurethanes. This process consists in reacting, in an organic solvent, an xe2x88x9d, w-dihydroxy polyester corresponding to the following formula (IV): 
in which:
R1, R2 and n are as defined above for the units of formula (I),
with an excess of a diisocyanate corresponding to the following formula (V):
Oxe2x95x90Cxe2x95x90Nxe2x80x94Rxe2x80x94Nxe2x95x90Cxe2x95x90O xe2x80x83xe2x80x83(V) 
in which R is as defined above for the units of formula (I),
and then in coupling the chains of the polyester polyurethane obtained above with a diol corresponding to the following formula (VI):
HOxe2x80x94Axe2x80x94OH xe2x80x83xe2x80x83(VI) 
in which:
A is as defined above for the units of formula (II),
at a temperature of between 40 and 100xc2x0 C. in the presence of a tin salt as catalyst.
The organic solvent used in the process according to the invention is preferably chosen from the group consisting of acetone, methyl ethyl ketone, tetrahydrofuran and 1,2-dichloroethane, these solvents being inert with respect to isocyanate groups.
The tin salt is preferably chosen from tin 2-ethylhexanoate and dibutyltin dilaurate.
The xcex1,xcfx89-dihydroxy polyester of formula (IV) used as starting material in the synthesis of the polyester polyurethanes according to the invention preferably has a molecular weight of between 400 and 5,000.
Among especially preferred xcex1,xcfx89-dihydroxy polyesters of formula (IV), there may be mentioned that in which R2 represents a bivalent radical of formula: 
and R1 represents xe2x80x94(CH2)3xe2x80x94 or a p-phenylene radical.
The diisocyanate of formula (V) used in the process according to the invention is preferably chosen from the group consisting of diphenylmethane 4,4xe2x80x2-diisocyanate and dicyclqhexylmethane 4,4xe2x80x2-diisocyanate (or dicyclohexylmethylene 4,4xe2x80x2-diisocyanate).
The diol of formula (VI) used in the process according to invention is preferably chosen from the group consisting of dimethylolpropionic acid and N-methyldiethanolamine.
According to a particular embodiment of the process according to the invention, a coupler corresponding to the following formula (VII):
Hxe2x80x94Bxe2x80x94Xxe2x80x94Bxe2x80x2xe2x80x94H xe2x80x83xe2x80x83(VII) 
in which:
B, Bxe2x80x2 and X are as defined above for the units of formula (III), is reacted in addition.
Preferably, the coupler is chosen from the group consisting of 1,3-diaminopropane and ethanolamine.
The polyester polyurethane obtained according to the above process is in non crosslinked form and can optionally be purified, for example by precipitation in a non-polar solvent such as cyclohexane.
The subject of the present invention is also, as a new industrial product, a stable pseudolatex consisting of particles of non crosslinked polyester polyurethane as defined and obtained above, neutralized using a neutralizing agent which can be either an inorganic or organic base when the radical A of the units of formula (II) is substituted with a carboxylic or sulphonic acid function, or an inorganic or organic acid when the radical A of the units of formula (II) is interrupted by a tertiary nitrogen atom, to a degree of neutralization of between 20 and 100%, the average diameter of the particles being between 5 and 300 nm.
According to the invention, the term xe2x80x9cpseudolatexxe2x80x9d is understood to mean a suspension consisting of generally spherical particles of the polyester polyurethane, these being obtained by dispersion of the polyester polyurethane in a suitable aqueous phase. The term xe2x80x9cpseudolatexxe2x80x9d should not be confused with the term xe2x80x9clatexxe2x80x9d or xe2x80x9csynthetic latexxe2x80x9d, which is also a suspension consisting of particles of a polymer, but in which the said particles are obtained directly by polymerization of one or more monomers in a suitable aqueous phase.
The pseudolatices according to the invention are obtained according to known methods of preparation of pseudolatices, subject, however, to certain features which will be mentioned below.
The conventional process for preparing pseudolatices consists in dissolving a water-insoluble polymer in an organic solvent which is soluble or partially soluble in water, in dispersing the dispersion thereby obtained in water while stirring and removing the organic solvent by evaporation under vacuum, which leads to a suspension consisting of particles of the polymer whose size is generally less than one micrometer.
According to this general process, the use of a surfactant, a mixture of surfactants or a protective colloidal polymer, or alternatively of a surfactants/protective colloidal polymer mixture, is essential for the purpose of obtaining good stabilization of the particles.
In contrast, the polyester polyurethanes according to the invention, containing partially or completely neutralized ionic functions, enable especially stable pseudolatices to be obtained in the absence of a hydrophilic stabilizer, a surfactant or a protective colloid.
It is self-evident that the acidic or basic nature of the neutralizing agent which it will be appropriate to use in order to neutralize the polyester polyurethane will be dependent on the nature of the ionic functions borne by the said polyester polyurethane.
When the polyester polyurethane contains a carboxylic or sulphonic acid function, the neutralizing agent can be an inorganic base such as sodium hydroxide, potassium hydroxide or ammonia solution, or an organic base such as an amino alcohol chosen from 2-amino-2-methyl-1-propanol (AMP), triethanolamine, triisopropanolamine (TIPA), monoethanolamine, diethanolamine, tris(2-hydroxy-1-propyl)amine, 2-amino-2-methyl-1,3-propanediol (AMPD) and 2-amino-2-hydroxymethyl-1,3-propanediol, or alternatively a diamine such as lysine.
When the polyester polyurethane contains a tertiary amine function, the neutralizing agent can be an inorganic acid such as hydrochloric acid or an organic acid such as lactic acid, glycolic acid or mandelic acid.
The neutralization may be carried either in situ in the solution of the polyester polyurethane in the organic solvent, by adding the specified amount of neutralizing agent, or during the preparation of the emulsion, the neutralizing agent then being in the aqueous phase of the emulsion. The organic solvent used must be a volatile solvent or a mixture of such solvents possessing a boiling point below that of water, and be miscible or partially miscible with water.
The organic solvent as defined above is preferably chosen from acetone, methyl ethyl ketone, tetrahydrofuran, methyl acetate, ethyl acetate, isopropanol and ethanol.
After the completely or partially neutralized polyester polyurethane has been obtained in the organic solvent, an emulsion is then prepared by pouring into the organic solution obtained, while stirring, a suitable amount of water optionally containing an antifoaming agent whose role will be to facilitate the subsequent evaporation of the organic phase.
According to a variant of the process as defined above, the neutralization of the ionic functions of the polyester polyurethane, dissolved in an organic solvent, may be carried out during the formation of the emulsion by pouring in an aqueous solution containing the requisite amount of the neutralizing agent.
During the formation of the emulsion, the stirring is preferably carried out using a shearing disperser of the Moritz or Ultra Turrax or Raineri type, equipped with deflocculating blades.
The emulsion thereby obtained is especially stable without it being necessary to employ a surfactant, inasmuch as the ionic groups of the polyester polyurethane place themselves at the interface with the water and protect the droplets from coalescence by electrostatic repulsion.
After formation of the emulsion at a temperature between room temperature and 70xc2x0 C. approximately, the organic solvent is then evaporated off under reduced pressure until it has been removed completely, the evaporation preferably being carried out under gentle heating.
A pseudolatex, that is to say an aqueous dispersion of particles of the film-forming polyester is polyurethane, is thereby obtained, which pseudolatex is free from any surfactant or from any other hydrophilic stabilizer while being very stable.
The average size of the particles of the pseudolatex and their polydispersity may be adjusted by varying, during the preparation of the said pseudolatex, the respective proportions between the polyester polyurethane, the organic solvent and water, thus modifying, in particular, the viscosity of the said pseudolatex and the sheen of the film obtained after evaporation. The average size of the particles also depends on the degree of neutralization and on the nature of the neutralizing agent.
According to a preferred embodiment of the pseudolatices according to the invention, the average size of the particles is between 10 and 250 nm.
The size polydispersity of the particles, measured by quasi-elastic light scattering, is generally less than 0.5 and preferably between 0.05 and 0.4.
The polyester polyurethanes according to the invention may be plasticized in order to improve film formation at room temperature. The plasticizing may he carried out by mixing the pseudolatex of polyester polyurethane according to the invention with an aqueous dispersion of a polyether polyurethane or polyester polyurethane having elastomeric character, these dispersions being of the same ionic nature as the polyester polyurethane according to the invention.
As dispersions of polyether polyurethanes having elastomeric character and of anionic nature, those sold under the names xe2x80x9cSancure 861xe2x80x9d or xe2x80x9cSancure 878xe2x80x9d by the company Sanncor, or under the name xe2x80x9cNeorez-R970xe2x80x9d by the company ICI, may be mentioned in particular.
As dispersions of polyester polyurethanes having elastomeric character and of ionic nature, that sold under the name xe2x80x9cNeorez-R974xe2x80x9d by the company ICI may be mentioned in particular.
The plasticizing may also be carried out using non-polymeric traditional plasticizers. It is then necessary for the plasticizer to be a good solvent for the polyester polyurethane according to the invention, and preferably to be insoluble in water. Among hydrophobic plasticizers, there may be mentioned, in particular:
diethyl, dibutyl and di-2-ethylhexyl phthalates and adipates,
diethyl and dibutyl tartrates,
diethyl, dibutyl and di-2-ethylhexyl phosphates,
propylene glycol derivatives chosen from propylene glycol phenyl ether, propylene glycol diacetate, dipropylene glycol butyl ether and tripropylene glycol butyl ether,
glycerol esters such as glyceryl triacetate (triacetin).
the propylene glycol monophenyl ether sold under the name xe2x80x9cDowanol PPHxe2x80x9d by the company Dow Chemical, and the dipropylene glycol n-butyl ether sold under the name xe2x80x9cdowanol DPnBxe2x80x9d by the Company Dow Chemical.
The plasticizer may be incorporated in a proportion ranging from 5 to 50% by weight relative to the total weight of the aqueous dispersion either after the production of the pseudolatex, or during the production of the pseudolatex when the emulsion is being formed, the plasticizer then being incorporated in the organic phase of the emulsion.
The subject of the invention is also a water-based cosmetic composition comprising as film-forming resin and preferably as the sole film-forming resin, the neutralized non crosslinked polyester polyurethane in the form of particles in an aqueous dispersion (pseudolatex) as defined above.
The proportion of pseudolatex in the cosmetic compositions is generally between 0.5 and 30%, and preferably between 1 and 25%, by weight relative to the total weight of the composition.
The cosmetic compositions according to the invention can take various forms, for example the form of make-up products for the nails or eyelashes such as nail varnishes or mascaras, and skin care products such as face packs or serums.
The compositions according to the invention can also take the form of hair care products such as styling shampoos, hair-end treatment lotions, hair lacquers and styling gels.
The compositions according to the invention can, in addition, contain UV-A or UV-B or broad-band sunscreen agents, and be used as antisun products.
The compositions according to the invention can contain, moreover, conventional cosmetic adjuvants chosen from fats, organic solvents, silicones, thickening agents, emollients, antifoaming agents, hydrating agents, humectants, nail hardeners, anionic, nonionic or amphoteric polymers or mixes thereof, antiperspirants, alkalinizing agents, colorants, pigments and propellent agents when the compositions take the form of an aerosol.
More specifically, as a fat, it is possible to use an oil or a wax or mixtures thereof, fatty acids, fatty alcohols, fatty acid esters such as C6 to C18 fatty acid triglycerides, petroleum jelly, paraffin, lanolin or hydrogenated or acetylated lanolin.
Among oils, mineral, animal and vegetable oils or synthetic oils may be mentioned, and in particular liquid petrolatum and paraffin, castor, jojoba and sesame oils, as well as Silicone oils and gums and isoparaffins.
Among animal, fossil, vegetable, mineral or synthetic waxes, beeswax, carob wax, candelilla wax, ozokerite and microcrystalline waxes may be mentioned, as well as silicone waxes and resins.
Among thickening agents, there may be mentioned:
cellulose derivatives such as hydroxyethylcellulose, methylcellulose, hydroxypropylcellulose and carboxymethylcellulose. Among these, the gums sold under the name xe2x80x9cCellosize QP 4400Hxe2x80x9d by the company Amerchol may be mentioned in particular,
carob gum, guar gum, the quaternized guar gum sold under the name xe2x80x9cJaguar C-13-Sxe2x80x9d by the company Meyhall, hydroxypropylguar gum, xanthan gum,
crosslinked polyacrylic acids such as those sold under the name xe2x80x9cCarbopolxe2x80x9d, by the company Goodrich,
crosslinked acrylic acid/(C10/C30) alkyl acrylate copolymers such as those sold under the names xe2x80x9cPemulen TR1xe2x80x9d and xe2x80x9cPemulen TR2xe2x80x9d by the company Goodrich,
the poly [glyceryl (meth) acrylate] polymers sold under the names xe2x80x9cHispagelxe2x80x9d or xe2x80x9cLubragelxe2x80x9d by the companies Hispano Quimica or Guardian,
polyvinylpyrrolidone,
polyvinyl alcohol,
the crosslinked acrylamide polymers and copolymers sold under the names xe2x80x9cPAS 5161xe2x80x9d or xe2x80x9cBozepol Cxe2x80x9d by the company Hoechst, xe2x80x9cSepigel 305xe2x80x9d by the company Seppic or xe2x80x9csalcare SC92xe2x80x9d by the company Allied Colloid, or alternatively
the crosslinked methacryloyloxyethyltrimethylammonium chloride homopolymers sold under the name xe2x80x9cSalcare SC95xe2x80x9d by the company Allied Colloid.
The compositions according to the invention find application most especially in nail care and treatment.
Thus, they can constitute a base coat for the subsequent application, after drying, of a traditional coloured nail varnish. The base coat thus protects the nail from the potentially damaging effect of the nail varnish solvent mixture, and prevents, moreover, the keratin of the nail from being coloured through the effect of the pigments. This base coat makes it possible, moreover, to improve the adhesion of the nail varnish, and can contain various active agents for nail care in so far as they are soluble in water or readily dispersable.
The advantage of using, according to this embodiment, a base coat of a composition according to the invention enables the nail varnish to be made strippable by simultaneous removal of the base coat and the nail varnish layer.
The compositions according to the invention can also constitute a top coat after application and drying of a traditional coloured nail varnish. This upper coat provides sheen and better mechanical resistance.
According to an especially preferred form, the compositions according to the invention take the form of coloured aqueous nail varnish.
These nail varnishes contain at least one pseudolatex as defined above in a proportion of 1 to 25% by weight, at least one thickening agent in a proportion of 0.01 to 5% and preferably of 0.1 to 1% by weight, at least one pigment in a proportion of less than 3% and preferably of between 0.5 and 2% by weight and at least one wetting agent in a proportion of 0.1 to 1% by weight, the remainder consisting essentially of water.
Several examples of preparations of polyester polyurethanes, and also of pseudolatices and cosmetic compositions containing them, will now be given by way of illustration of the invention.